This invention relates to a sheet separating apparatus for removing sheets one by one from a stack of sheets.
The invention has application, for example, to a currency note picking apparatus for extracting notes from a currency cassette used in an automated teller machine (ATM). As is well known, in operation of an ATM a user inserts a customer identifying card into the machine and then enters certain data (such as codes, quantity of currency required or to be paid in, type of transaction, etc.) upon one or more keyboards associated with the machine. The machine will then process the transaction, update the users account to reflect the current transaction, dispense cash, when requested, extracted from one or more currency cassettes mounted in the machine, and return the card to the user as part of a routine operation.
One known type of sheet separating apparatus is described in European Patent Application No. 0 448 385. Vacuum operated picking devices apply suction force to the end note in a stack of notes in a cassette, and move the notes towards rollers which hold the notes while the suction force is removed. The rollers then move the notes to the cash dispensing part of the apparatus.
In this example, the suction force is removed by venting the suction device to the atmosphere. Inevitably, dust and grit are drawn into the system from the atmosphere, and the associated vacuum pump initially becomes inefficient, and eventually fails. Depending on the environment, the period between failures varies from about a year in relatively clean atmospheres to as little as a week in atmospheres with a high percentage of dust or even sand. Repairing the apparatus on a frequent basis is, of course, expensive. Even if a filter is provided between the pump and the atmosphere, then, in dusty environments, a minimum of three failures each year can still be expected, which is unacceptably frequent.